Definitions for "SCRUB RADIUS"
A term relating to steering axis inclination, this feature minimizes any tendency for the vehicle to pull when braking during a turn. Positive scrub radius is when a line drawn through the steering axis intersects the road surface inside of the tire centerline. Negative scrub radius is when a line drawn through the steering axis intersects the road surface outside of the tire centerline.
The distance at the road surface between the tire line and the SAI line extended downward through the steering axis. The line through the steering axis creates a pivot point around which the tire turns. If these lines intersect at the road surface, a zero scrub radius would be present. When the intersection is below the surface of the road, this is positive scrub radius. Conversely, when the lines intersect above the road, negative scrub radius is present. The point where the steering axis (sai) line contacts the road is the fulcrum pivot point on which the tire is turned. Here is a diagram explaining scrub radius.
The distance from the point where the steering axis intersects the ground to the longitudinal line that runs through the center of the tire's contact patch. Also called "steering offset."